Add socketKeepAlive configuration property for Elasticsearch

See gh-32051

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/elasticsearch/ElasticsearchProperties.java

@@ -62,6 +62,11 @@ public class ElasticsearchProperties {
 	 */
 	private String pathPrefix;
 
+	/**
+	 * Whether to enable socket keep alive between client and Elasticsearch.
+	 */
+	private boolean socketKeepAlive = false;
+
 	private final Restclient restclient = new Restclient();
 
 	public List<String> getUris() {
@@ -112,6 +117,14 @@ public class ElasticsearchProperties {
 		this.pathPrefix = pathPrefix;
 	}
 
+	public boolean isSocketKeepAlive() {
+		return this.socketKeepAlive;
+	}
+
+	public void setSocketKeepAlive(boolean socketKeepAlive) {
+		this.socketKeepAlive = socketKeepAlive;
+	}
+
 	public Restclient getRestclient() {
 		return this.restclient;
 	}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/elasticsearch/ElasticsearchRestClientConfigurations.java

@@ -27,6 +27,7 @@ import org.apache.http.auth.UsernamePasswordCredentials;
 import org.apache.http.client.config.RequestConfig;
 import org.apache.http.impl.client.BasicCredentialsProvider;
 import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
+import org.apache.http.impl.nio.reactor.IOReactorConfig;
 import org.elasticsearch.client.RestClient;
 import org.elasticsearch.client.RestClientBuilder;
 import org.elasticsearch.client.sniff.Sniffer;
@@ -155,6 +156,8 @@ class ElasticsearchRestClientConfigurations {
 		@Override
 		public void customize(HttpAsyncClientBuilder builder) {
 			builder.setDefaultCredentialsProvider(new PropertiesCredentialsProvider(this.properties));
+			map.from(this.properties::isSocketKeepAlive).whenTrue()
+					.to(keepalive -> builder.setDefaultIOReactorConfig(IOReactorConfig.custom().setSoKeepAlive(keepalive).build()));
 		}
 
 		@Override

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/elasticsearch/ElasticsearchRestClientAutoConfigurationTests.java

@@ -183,6 +183,23 @@ class ElasticsearchRestClientAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	void socketKeepAliveDefaults() {
+		RestClient client = RestClient.builder(new HttpHost("localhost", 9201, "http")).build();
+		assertThat(client.getHttpClient()).extracting("connmgr.ioReactor.config.soKeepAlive").isEqualTo(Boolean.FALSE);
+	}
+
+	@Test
+	void configureWithCustomSocketKeepAlive() {
+		this.contextRunner.withPropertyValues("spring.elasticsearch.socket-keep-alive=true").run(
+				context -> {
+					assertThat(context).hasSingleBean(RestClient.class);
+					RestClient client = context.getBean(RestClient.class);
+					assertThat(client.getHttpClient()).extracting("connmgr.ioReactor.config.soKeepAlive").isEqualTo(Boolean.TRUE);
+				}
+		);
+	}
+
 	@Test
 	void configureWithoutSnifferLibraryShouldNotCreateSniffer() {
 		this.contextRunner.withClassLoader(new FilteredClassLoader("org.elasticsearch.client.sniff"))